I'm not convinced the maturity issues are overblow. I suspect your response to this question is the same as it would've been had we asked it about Rasmus - nobody ever wants to accept the fact that a kid is acting like a kid until it bites them in the ass.
That said, even assuming they are overblown - why are we so quick to state that he's the best option for this team right now?
Sure, he had a great season in AA. Fantastic - when Matt Adams was in AA, his was just as good. More critically, Matt Adams then went to AAA and got even better last season. 18 bombs in 258 ABs to go with a .986 OPS and a .329 BA is filthy. That's world-class power paired with outstanding bat control.
Additionally, as Adams has already started his service clock, there's no loss of team control by brining him north to start the year and playing him every day.
Next, compare their respective springs. Matt Adams has had a better one and against better pitching (pitcher quality index of 8.3 for Taveras, 8.8 for Adams). Better OBP, better SLG%, better at driving runs in - he's just flat been a better hitter than Taveras.
Finally - we aren't trading Taveras but we might trade Adams. If we hope to really get a haul for him, we need to establish his value against major league hitters - we can't do that from the bench.
This organization is better served in both the near term and long term to start Matt Adams at 1b and Allen Craig in RF to begin the year. It's helps a great deal financially by retaining the year of team control. It helps from a trade-value perspective by pumping up Adams value a bit. It helps from a pure production standpoint by putting the more polished and powerful hitter on the field to make up for the loss of Beltran and Freese. And all of that sets aside any ounce of 'maturity' concerns, though I would be very reticent to so quickly dismiss them.
It's just the right move to make.
If you can't draw a crowd, draw dicks on the wall.